Forest fire video monitoring system and method

ABSTRACT

The invention relates to the forest video monitoring. A method and system are provided for automatically binding a video camera to the absolute coordinate system and determining changes in the video camera binding. In one aspect, the method comprises the steps of: in each of at least two predetermined time moments, aiming the video camera at an object a position of which in the absolute coordinate system centered in a point in which the video camera resides is known at said moment, and determining an orientation of the video camera in a native coordinate system of the video camera; and, based on the determined orientations of the video camera and positions of the object, calculating a rotation of the native coordinate system of the video camera in the absolute coordinate system. The calculated rotation of the video camera&#39;s native coordinate system is used to recalculate coordinates of an observed object from the video camera&#39;s native coordinate system into the absolute coordinate system. The technical result relates to the improved accuracy of locating the observed object.

FIELD OF THE INVENTION

The present invention relates generally to the field of videosurveillance, and more particularly, to a system and method for videomonitoring of forests, which, in general, provides the ability tomonitor large forest areas for early detection of forest fires forfurther localization and extinguishing.

BACKGROUND ART

The forest fire video monitoring systems intended for detecting andlocating forest fires are relatively new. However, their importance isever growing, as the problem of forest fires can rightly be consideredas one of the most serious and unresolved human problems at the moment.Forest fires occur and cause great damage in many countries of theworld, as evidenced by wildfires in Russia in summer of 2010 which haddisastrous consequences, including failure to comply with earlydetection and location of the fires, as widely discussed in detail inmass media.

In a typical case illustrated in FIG. 1, the forest fire videomonitoring system 100 includes one or more remotely controlled videomonitoring points 110 and one or more associated automated operatorworkstations 120 to properly operate the video monitoring points 110.

The equipment 120 of an automated operator workstation, in general, isbased on well-known computer and communication technologies, and ittypically comprises a computer with special and general purpose softwarethat is configured for remote data exchange. Hardware and generalpurpose software (e.g., operating system) forming part of such acomputer are well known in the art. Thus, the term “computer” can referto a personal computer, a laptop, a set of interconnected computers,etc. with characteristics that meet the requirements of the system 100.The computer has a display device coupled thereto that displays, whenthe computer is operated, a graphical user interface (GUI) associatedwith a specialized application by which the operator visually monitorsthe territory and controls the video monitoring points 110. Interactionwith the elements of the graphical user interface is performed by meansof well-known input devices connected to the computer, such as keyboard,mouse, etc.

Such an operator workstation can be arranged in a specialized controland monitoring center. The presence of multiple workstations 120 allowsto distribute the load among multiple operators to thereby improve thequality of detection.

Each video monitoring point 110 is substantially a transmission-sideequipment 111 arranged on a high-rise construction 112.

The high-rise construction 112, in general, can be any high-riseconstruction which meets the requirements imposed on the system 100(i.e. adapted to accommodate the transmission-side equipment at asufficient height and configured to inspect large areas), and is usuallya communication service provider tower, mobile operator tower,television tower, lighting tower, etc.

Generally, the term “transmission-side equipment” 111 denotes equipmentwhich is arranged on the high-rise construction 112 and comprises acontrolled video device 113 and a communication module 114 forcommunication/data exchange with the operator workstation(s) 120.

The controlled video device 113 is generally a digital video camera 115(i.e., a device that converts electromagnetic waves of the opticalrange, or of a range close to the optical range, into an electricalsignal) equipped with a zoom 116 (i.e., with an appliance designed forzooming in/out an acquired image) and mounted on the rotating device 117which enables to mechanically change the orientation of the video camera115 with high accuracy.

The transmission-side equipment 111 also includes a camera control unit118 connected to the communication module 114, the video camera 115, thezoom 116, and the rotating device 117, and intended for general controlover the functions of the controlled video device 113 as a whole and itscomponents in particular. In this manner, upon receipt of controlsignals from the operator via the communication module 114, the controldevice 118 is adapted to set the required spatial orientation of thecamera 115 (for example, to aim it at an object to be monitored), byoperating the rotating device 117, and/or to perform zooming in/out ofthe picture of the object under surveillance from said camera, byoperating the zoom. In addition, the control unit 118 is adapted todetermine the current spatial orientation of the video camera 115 andprovide data on its current spatial orientation through thecommunication module 114 to the requesting party (in particular, to theoperator workstation 120 where the data, for example, is displayed inthe graphical user interface). The functional capabilities listed hereare the well-known properties of modern controlled video cameraassemblies available on the market.

Generally, the control device 118 is a microprocessor-based hardwareunit, like a controller or a microcomputer, programmed in a known mannerand/or programmable to perform the functions assigned to it, whichshould be obvious to those skilled in the art. The programming of thecontrol unit 118 can be performed, for example, by flashing itsfirmware, which is well known in the art. Accordingly, the video cameracontrol device 118 is typically connected to a storage device (e.g., anintegrated flash memory) which stores the related software or firmwarewhich, when executed, implements the functions associated with thecontrol device 118.

The operator workstations 120 may be connected to the monitoring points,both directly and via a communication network (e.g., a network 130)using well-known and broadly used wired and/or wireless, digital and/oranalog communications technologies, and thus the communication module114 of the video monitoring point and the computer communicationinterface of the operator workstation 120 should meet the communicationstandards/protocols for establishing such a communication link.

The exemplary network 130, to which the video monitoring points and theworkstations 120 are connected, can be an address network, such as theInternet. If the video monitoring point 110 is near a communicationchannel belonging to an external provider, which is commonplace, then itis preferable to use this channel to connect the transmission-sideequipment 111 to the Internet. If the video monitoring point 110 can notbe connected directly to the Internet, then the well-known wirelessbroadband technologies (e.g. WiFi, WiMAX, 3G, etc.) are used forcommunication between the transmission-side equipment 111 and anInternet access point. In a similar way, the operator workstations 120are connected to the network 130. For example, depending on theimplemented access technology, a modem (including a wireless one), anetwork interface card (NIC), a wireless access card, etc., which can beexternal or internal in relation to the computer of the operatorworkstation 120, can be used for connecting to the network 130.

The system 100 also preferably includes a server 140 which is connectedto the network 130 and which is delegated with the functions ofcentralized management over the totality of video monitoring points 110and their interaction with the operator workstations 120 to ensurereliable operation of the system 100. The server 140 is usually ahigh-performance computer or a set of interconnected computers (forexample, a blade server chassis) having specialized server softwareinstalled thereon and a high speed (e.g. optical) connection to theInternet. The hardware/software implementation of such a server isobvious to those skilled in the art. In addition to the generalfunctions of managing the system 100, the server 140 can perform avariety of highly specialized functions—for example, it can operate as avideo server that provides intermediate data processing and sends theprocessed data to a user upon request.

The description of specific implementations of data/signal exchangebetween the video monitoring points 110, the operator workstations 120,and the server 140 via the network 130 is omitted, because they arewidely known in the art.

With such a method of implementing the forest fire video monitoringsystem, a single user is able to monitor a large enough controlledterritory, while manipulating multiple cameras at a time. In addition,due to the above characteristic functional capabilities, the ability isprovided to automatically quickly locate the source of fire visible frommultiple cameras, using the well-known azimuth method, and to store inmemory (e.g., in the server 140 or in the computer of the operatorworkstation 120) predefined patrol paths for quick access thereto andmonitoring thereof Here, “patrol path” refers to a predefined sequenceof changing the camera orientation to obtain visual informationregarding the required predetermined area.

It should be noted that performance of modern electronic hardware allowsto create based thereon imaging and control devices among the componentsof the forest fire video monitoring system with a wide userfunctionality, which greatly simplifies the operator's work. Inaddition, modern hardware, with special software executable thereby, cantake over some of the functions of automatic detection of potentiallydangerous objects on video or still images obtained from the videocameras (when monitoring forests, such objects may be smoke, fire,etc.). Such computer vision systems intended to find dangerous objectsin images can use a priori information about the features of smoke orfire, for example, specific movement, color, brightness, etc., or otherindicia of fire, for example, they can detect warm air from fire with athermal imager, or they are able to detect emissions of certain gaseswith a gas analyzer. Such computer vision systems are used in manyindustries, ranging from robotics to security systems, which isdescribed in detail, for example, in “Computer Vision: Modern Approach”,David Forsyth and Jean Ponce, Williams Publishing, 2004, 928 sheets. Inthis context, an intrinsic characteristic of automatic detection basedon computer vision is the probability of false alarm and target missingthat must be reduced by all means in each video monitoring system.

Such an intelligent subsystem that implements the indicated computervision technologies can be also deployed in the operator workstation120, the server 140, and even in the controlled video device 113 itself.

Above is the generalized structural description of a typical modernforest fire video monitoring system which operates based on the usage ofcontrolled video cameras. The given generalized description is notimplied as exhaustive and is just intended for assistance in betterunderstanding of the invention which is described in detail below.

The known examples of such forest fire video monitoring systems areForestWatch (Canada), IPNAS (Croatia) and FireWatch (Germany). Similarsystems have been developed in the Russian Federation (for example,“Klen”, “Baltika”, “Lesnoi Dosor”).

It should be noted that development and deployment of such forest firevideo monitoring systems has become possible only in last few years.Only now, the number of cell communication towers is such that theycover the main fire risk areas, thereby minimizing infrastructure costs.In addition, broadband Internet services have also become much moreaffordable, which allows to exchange with large amounts of informationand transmit real-time video over the Internet, and the cost ofequipment for wireless communications over long distances has reduced.It should be further noted that detection of forest fires with camerasstarted from the beginning of century XXI, but the systems proposed bythat time were composed of primitive rotatable cameras and theoperator's screen which was to be in close proximity to the point ofvideo monitoring. In practice, the proposed systems could not be scaledup and used for detecting fires even within a single forest district,not to mention big regions.

The following shortcomings are typical to the existing forest fire videomonitoring systems.

1. The Problem of Accuracy of Determining Visible Object Coordinates

The accuracy of determination of coordinates of a visible object isdefined by such parameters as:

the accuracy of locating a video camera (the accuracy of binding thevideo camera to the terrain);

the accuracy of binding the video camera orientation to the coordinatesystem relative to the north and the angle of deviation from themathematical horizon (the vertical angle).

As noted above, the rotating device enables to change the cameraorientation—such rotating devices make it possible to change, within acertain range, the vertical and horizontal angles, i.e. the video cameradirection is actually changed in the spherical coordinate system whichis bound directly to the rotating device (i.e. in the native coordinatesystem of the video camera.)

When installing and operating the video camera, it is necessary todetermine the orientation of the camera's native coordinate systemrelative to the spherical coordinate system the center of which issituated in the location of the video camera, the unit vector with thecoordinates (φ=0, θ=0, ρ=1 coincides with the north direction, and theunit vector with the coordinates (φ=0, θ=−90°, ρ=1 coincides with thevertical (in astronomy such coordinate system is called topocentric orhorizontal, here this system of coordinates will be referred to as the“absolute coordinate system of the video camera”).

The current location of the video camera can be determined quiteaccurately, for example, using the modern GPS-based means.

The accuracy of determination of the current orientation of the videocamera in its native coordinate system can also be rather high, which isprovided by modern rotating devices (up to 0.1-0.05′, as, for example,in the case of controlled video cameras manufactured by AXIS), and thisaccuracy is ever growing with development of technology.

At the same time, it is almost impossible to eliminate the problemsassociated with the accuracy of binding the video camera's nativecoordinate system to the absolute coordinate system—namely this bindingis responsible for the final accuracy of locating a visible object. Thisproblem is caused by complexity of the original binding (when mountingthe video camera) and the sub-binding during the system operation thatis necessitated by structural deformations of the high-rise constructionon which the camera is fixed, by the nonideal fixing of the camera, andother factors.

2. High Probability of False Alarms

When using of the computer vision subsystem briefly described above, animportant factor is the capability of validating (i.e., acknowledging)potentially dangerous objects. This confirmation can be accomplished,for example, by the operator that filters out the false detectedobjects. This validation facilitates operation of the automaticsubsystem, since in the case of subsequent detection of a dangerousobject in the same direction, the subsystem can use the informationentered by the operator about the type of said object. The operation ofsuch an algorithm must be based on the possibility of determining theexact current orientation of the video camera, so that later, when anobject is detected in the same direction (i.e., substantially the sameobject), said object is excluded from the class of dangerous objects.

To perform this function, it is necessary to accurately determine thatthe current camera direction coincides with the one that has beenvalidated by the user, with the accuracy sufficient for operation of thesubsystem. This procedure is rather difficult, because, as mentionedabove, the video camera, being fully adapted for rigid fixation on therigid structure of the high-rise construction, can not provide completestillness, that is, the orientation of the camera's native coordinatesystem displaces, and therefore, the accuracy of the filtering procedureis related to the accuracy of determination of the current direction.

This becomes especially urgent in detecting faraway (more than 15 km)objects when the angular size of the object is small enough (less than1′): in this case, even a small deviation of the camera will causeincorrect estimation of the location of said object.

3. Failure to Locate an Object Visible from only One Camera

This problem occurs in the boundary areas where it is not possible oreconomically feasible to place at least a second camera to locate adangerous object. In addition, failure to at least approximatelydetermine the location of the object with a single video camera makes itdifficult to find said object with another video camera from which itcan also be seen.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a forest fire videomonitoring system and a method implemented thereby that automaticallybind the video camera's native coordinate system to the absolutecoordinate system associated with the video camera, in order to improvethe accuracy of locating the observed object. The system and methodaccording to this object substantially address the first of theshortcomings listed above.

According to the aspect corresponding to said object, a forest firevideo monitoring system is provided. The system comprises: at least oneremotely controlled video monitoring point; and at least onecomputerized operator workstation for operating said video monitoringpoint. The system may further comprise a server, wherein the videomonitoring points, the server, and the operator workstations arecommunicatively interconnected (e.g., an address network).

The remotely controlled video monitoring point includes: a high-riseconstruction; and a transmission-side equipment residing on thehigh-rise construction. The transmission-side equipment comprises: avideo camera on a rotating device; and a camera control unit configuredto determine a current spatial orientation of the video camera in anative coordinate system of the video camera. The video camera isequipped with a zoom.

The proposed forest fire video monitoring system also comprises acomputer-implemented module configured, in each of at least twopredetermined time moments, to obtain an orientation of the video cameraaimed at a known astronomical object, the orientation determined by thecamera control unit in the native coordinate system of the video camera,and to determine, based on a predetermined location of the videomonitoring point and said time moment, a position of the astronomicalobject in an absolute coordinate system centered in a point in which thevideo camera resides. The computer-implemented module is also configuredto calculate, based on the determined orientations of the video cameraand positions of the astronomical object, a rotation of the videocamera's native coordinate system in the absolute coordinate system.

The computer-implemented module may reside in the server, and/or in theoperator workstation, and/or in the transmission-side equipment of thevideo monitoring point.

The astronomical object is preferably Sun, and the location of the videomonitoring point is determined by its geographical coordinates, whilethe position of the astronomical object is determined by its azimuth andangular altitude above the horizon.

The camera can be aimed at the astronomical object by manually matchingthe center of an image obtained from the video camera with the center ofthe astronomical object.

The proposed system may further comprise a computer-implementedintelligent subsystem configured, based on computer vision technologies,to aim the video camera at the astronomical object by automaticallydetecting the astronomical object based on analysis of an image obtainedfrom the video camera, and automatically matching the center of theimage obtained from the video camera with the center of the astronomicalobject.

When aiming the video camera at the astronomical object, the zoom ispreferably used to zoom in the astronomical object to the maximumpossible extent.

A method implemented by the proposed forest fire video monitoring systemis provided for automatically binding a native coordinate system of avideo camera to an absolute coordinate system, the method comprising: ateach of at least two predetermined time moments, aiming the video cameraat a known astronomical object, and determining an orientation of thevideo camera in the native coordinate system of the video camera; anddetermining, based on a predetermined location of the video monitoringpoint and said time moment, a position of the astronomical object in anabsolute coordinate system centered in a point in which the video cameraresides. Then, the method comprises calculating, based on the determinedorientations of the video camera and positions of the astronomicalobject, a rotation of the video camera's native coordinate system in theabsolute coordinate system.

Based on the calculated rotation of the video camera's native coordinatesystem, it is possible to perform recalculation of coordinates of anobserved object from the video camera's native coordinate system intothe absolute coordinate system.

It should be emphasized that, according to the aspect underconsideration, said astronomical object may be, as a matter of fact,represented by any discernible object whose position in the absolutecoordinate system camera is known at a given time moment.

Another object of the invention is to provide a forest fire videomonitoring system and a method implemented thereby which determine achange in binding of a video camera in order to accurately determine itscurrent direction while filtering out non-dangerous objects. In fact,the system and method according to this object substantially address thesecond of the shortcomings listed above.

According to the aspect corresponding to this object, a forest firevideo monitoring system is provided that comprises the same componentsas listed above in relation to the preceding aspect. The proposed systemfurther comprises a data store to store orientations of the camera inthe video camera's native coordinate system, the orientations determinedby the camera control unit upon aiming the camera at each of at leasttwo predefined discernible still objects in the terrain. Thecomputer-implemented module in the system is configured, for each ofsaid objects, to receive a current orientation of the video camera inthe camera's native coordinate system, the current orientationdetermined by the camera control unit upon re-aiming the video camera atsaid object. The computer-implemented module is also configured, basedon the received current orientations of the video camera and therespective stored orientations of the video camera, to calculate arotation of the video camera's native coordinate system.

Preferably, the computer-implemented module is further configured, whencomparing a current orientation of the video camera aimed at an observedobject, with a stored orientation of the video camera when aimed at apreviously analyzed object, to adjust said stored orientation of thecamera based on the calculated rotation of the video camera's nativecoordinate system.

The method implemented by the proposed forest fire video monitoringsystem is provided for determining a change in binding of a videocamera, the method comprising: aiming the video camera at each of atleast two predefined discernible still objects in the terrain, anddetermining an orientation of the video camera in a native coordinatesystem of the video camera. Then, the determined orientations of thevideo camera are stored. After that, for each of said objects, thecamera is aimed according to the stored orientation of the video cameracorresponding to said object, and, in case of deviation of the camerafrom the object, the camera is re-aimed at the object, and a currentorientation of the camera in the video camera's native coordinate systemis determined. Finally, based on the determined current orientations ofthe video camera and the respective stored orientations of the videocamera, a rotation of the video camera's native coordinate system iscalculated. When comparing a current orientation of the camera aimed atan observed object with a stored orientation of the video camera whenaimed at a previously analyzed object, this stored video cameraorientation can be adjusted based on the calculated rotation of thevideo camera's native coordinate system.

Yet another object of the present invention is to provide a forest firevideo monitoring system and a method implemented thereby which are usedto determine the distance to an observed object using one video camerawith sufficiently high accuracy. The system and method according to thethis object substantially address the third of the above shortcomings.

BRIEF DESCRIPTION OF THE FIGURE DRAWINGS

The above and other aspects and advantages of the present invention aredisclosed in the following detailed description, with reference to thedrawings in which:

FIG. 1 is a schematic partial view of the forest fire video monitoringsystem,

FIG. 2 is an illustrative flowchart of the method for automaticallybinding the video camera's native coordinate system to the absolutecoordinate system according to the present invention,

FIG. 3 illustrates the Euler angles,

FIG. 4 is an illustrative flowchart of the method for determining achange in binding of the video camera's native coordinate systemaccording to the present invention;

FIG. 5 is an illustrative flowchart of the method for filtering observedobjects in patrolling.

DETAILED DESCRIPTION OF THE INVENTION

In the following disclosure of the present invention, reference will bemade to the forest fire video monitoring system 100 of FIG. 1, where thedescription of said system fully relates to disclosure of the presentinvention. In this section, in order to avoid unnecessary repetitionsand cumbersome description, the components of the video monitoringsystem 100, which are generally typical to the prior art systems, willnot be described again in detail.

Furthermore, the disclosure of the present invention is presented insubsections corresponding to the objectives stated above.

1. Automatic Binding of the Video Camera'S Native Coordinate System tothe Absolute Coordinate System

Referring to FIG. 2, there is described the method 200 implemented inthe video monitoring system (such as the system 100 of FIG. 1) forautomatically binding the video camera's native coordinate system (CS)to the absolute coordinate system.

In astronomy, the methods are known to determine, with high accuracy,horizontal (topocentric) coordinates (i.e., azimuth (the angle from thenorth direction) and angular altitude (the angle from the mathematicalhorizon)) of various celestial bodies, such as Sun, based ongeographical coordinates of the observer and the exact time of day. Thewidespread use of these methods is known, in particular, in marinenavigation.

In step 202, the video camera 115 is aimed at a known astronomicalobject (such as Sun, Moon, etc.).

The camera 115 can be aimed manually, that is, the operator detects theastronomical object when viewing the area and points the video camerathereto, such that the center of the image acquired from the cameramatches the center of said object. In an exemplary embodiment, this isaccomplished by interaction of the operator, using input devices, withthe respective elements of the graphical user interface displayed in thedisplay device, so that the computer of the operator workstation 120generates control commands sent over the network 130 (possibly throughthe server 140 and with its direct participation) to the appropriatetransmission-side equipment(s) 111, where those commands are deliveredthrough the communication module 114 to the camera control unit 118which generates based on said commands the control signals for drivingthe rotating device 117 to set such a spatial orientation of the camera115 that it is aimed at the respective astronomical object.

This procedure can be also performed automatically, that is, in theautomatic mode the video camera 115 views the area and, by means ofspecial computer vision algorithms implemented in the system 100, asnoted above, detects an object with characteristics known in advance(for example, in the case of Sun it will be a bright circle).

When aiming the video camera 115 at the astronomical object, theastronomical object is preferably zoomed in to the maximum possibleextent (to this end, in the exemplary embodiment, the camera controldevice 118 appropriately controls the zoom 116) and the center of theimage obtained from the camera is manually or automatically aligned withthe center of the astronomical object.

The location of the astronomical object can be estimated with theaccuracy of up to several tenths/hundredths of a degree. In particular,the angular size of Sun is about 31′27″. Modern cameras can achievemagnification at which the viewing angle is V. Computer visiontechniques allow to determine the center position of the circle in theimage with the accuracy of up to few pixels. That is, if the videocamera has the resolution of one or more megapixels, then the accuracyof determination of the direction to Sun may be about 0.05″.

Upon aiming the camera at the astronomical object, step 204 determinesthe orientation of the camera in its native coordinate system, i.e. thedirection of the camera in its native coordinate system associated withthe mechanics of the video camera. As mentioned above, suchfunctionality is provided in modern controlled video cameras andimplemented, for example, by the camera control device 118.

In step 206, based on the known exact location of the video monitoringpoint 110, the position of the astronomical object is determined in thevideo camera's absolute coordinate system at the current time. Asmentioned above, in astronomy, there are known methods and formulaswhich enable to determine, from the known geographic coordinates of theobserver and the exact time of day, azimuth and altitude of theastronomical object, that is, the coordinates of the object in thehorizontal coordinate system.

The procedure according to steps 202-206 should be performed repeatedly,where successive performances are separated by a certain period of time.The minimum number of performances is two, which follows from thedetailed discussion presented hereinbelow. At the same time, in order toimprove accuracy, said procedure may be performed more times, since,despite possibly high precision of the devices, each measurement assumesa certain error which can be reduced by repeatedly performing saidmeasurements/determinations.

It is mostly convenient to carry out this procedure on such astronomicalobject as Sun. In this case, the video camera can be aimed at Suntwice—just after sunrise and before sunset, when brightness issufficient for detection, but not too high for causing various glares onthe lens and damaging electronics of the video camera. It should beemphasized once again that in each of these two time moments the videocamera is aimed at Sun (step 202), its orientation is determined in thenative coordinate system (step 204), and the position of theastronomical object is determined in the absolute coordinate system,knowing the exact time corresponding to said time moment and the precisegeographical coordinates of the video camera (step 206).

Based on the video camera orientations and positions of the astronomicalobject, as determined in steps 204 and 206, step 208 calculates arotation of the video camera's native coordinate system in the absolutecoordinate system associated with it. The calculated rotation of thevideo camera's native coordinate system allows to determinerecalculation coefficients for coordinates of an observed object fromthe video camera's native coordinate system into the absolute coordinatesystem.

In fact, the following correspondences are achieved: vertical andhorizontal (panoramic) angle in the video camera's native coordinatesystem—altitude of the astronomical object (for example, Sun) above themathematical horizon (vertical angle in the absolute coordinate system)that is bound to the location of the camera (observer), and azimuth(horizontal angle in the absolute coordinate system) bound to thelocation of the video camera.

For further recalculation from the video camera coordinate system intothe absolute (horizontal) coordinate system, it is necessary, based onthe correspondence data, to determine the rotation of the nativecoordinate system in the absolute coordinate system, and, to this end,the Euler angles can be determined, for example. The Euler angles arethe angles describing rotation of a perfectly rigid body in thethree-dimensional Euclidean space.

Upon determination of the Euler angles, it is possible to obtain, foreach point in the native coordinate system, the value in the absolutecoordinate system, which means that for every visible object we canrecalculate the obtained direction to said object in the absolutecoordinate system associated with the location of the camera, i.e., infact, eliminate the influence of the above factors on the accuracy ofdetermination of the observed object direction.

Mathematically, this is expressed as follows.

We obtain two correspondences of two observation points in thehorizontal coordinate system (azimuth (a), altitude (v)) to two pointsin the video camera's native coordinate system (panoramic angle (p),vertical angle (t)):

(a1, v1)−(p1, t1),

(a2, v2)−(p2, t2).

According to the example given above, these points can correspond to thetwo aimings of the video camera at Sun.

Based on this, it is necessary to obtain three Euler angles e1, e2, e3,i.e.

e1=f1(a1, v1, p1, t1, a2, v2, p2, t2),

e2=f2(a1, v1, p1, t1, a2, v2, p2, t2),

e3=f3(a1, v1, p1, t1, a2, v2, p2, t2).

Then, knowing the three Euler angles, we obtain for each (p, t) thecorrespondence (a, v), i.e.

a=f1(p, t, e1, e2, e3),

v=f2(p, t, e1, e2, e3).

Let us dwell on the problem of coordinate recalculation anddetermination of the Euler angles.

Direct Problem

The correspondence between the visible object coordinates in the videocamera's native coordinate system (p, t), where p—panoramic angle,t—vertical angle, and the absolute coordinates (a, v), where a—azimuth,v—angular altitude above the mathematical horizon, is defined by theEuler angles α, β, γ which in this case describe the rotation(orientation) of the video camera's native coordinate system in theabsolute coordinate system. FIG. 3 schematically shows the Euler angles.The “binding of the camera” or “binding of the camera's nativecoordinate system” in this application substantially refers to a certainorientation (rotation) of the video camera's native coordinate system inthe absolute coordinate system, as described by the Euler angles.

The Euler angles allow to map any position of the system to the currentposition. Let us denote the initial coordinate system as (x, y, z), andthe final one as (X, Y, Z). The intersection of the coordinate planes xyand XY is called the nodal line N, where:

angle α is the angle between the axis x and the nodal line.

angle β is the angle between the axes z and Z.

angle γ is the angle between the axis X and the nodal line.

The rotations of the coordinate system by these angles are calledprecession, nutation and intrinsic rotation (spin). These rotations arenon-commutative, and the final position of the system depends on theorder in which the rotations are performed. In the case of the Eulerangles, it is represented by the sequence 3, 1, 3 (Z, X, Z) (See FIG.3).

Upon determination of the Euler angles, the rotation matrix iscalculated, based on which the angles (a, v) are uniquely determined foreach pair (p, t). The matrix of rotation of the Cartesian coordinatesfor the Euler angles is as follows:

${M\left( {\alpha,\beta,\gamma} \right)} = \begin{pmatrix}{\cos \; {\alpha cos\beta}} & {{\cos \; {\alpha sin\beta sin\gamma}} - {\sin \; {\alpha cos\gamma}}} & {{\cos \; {\alpha sin\beta cos\gamma}} + {\sin \; {\alpha sin\gamma}}} \\{\sin \; {\alpha cos\beta}} & {{\sin \; {\alpha sin\beta sin\gamma}} + {\cos \; {\alpha cos\gamma}}} & {{\sin \; {\alpha sin\beta cos\gamma}} - {\cos \; {\alpha sin\gamma}}} \\{{- \sin}\; \beta} & {\cos \; {\beta sin\gamma}} & {\cos \; {\beta cos}\; \gamma}\end{pmatrix}$

To use this matrix, the angles (p, t) must be converted to the Cartesiancoordinate system. The angle p corresponds to the angle φ in thespherical coordinate system, and the angle θ=π/2+t. The radius of thesphere is not important, because its size does not change when rotating,so r=1. The coordinates in the Cartesian coordinate system aredetermined as:

$\quad\left\{ \begin{matrix}{{x = {r\; \sin \; {\theta cos\phi}}},} \\{{y = {r\; \sin \; {\theta sin\phi}}},} \\{z = {r\; \cos \; {\theta.}}}\end{matrix} \right.$

In multiplying the rotation matrix to the column vector

$\begin{pmatrix}x \\y \\z\end{pmatrix},$

the column vector is

$\quad\begin{pmatrix}x_{1} \\y_{1} \\z_{1}\end{pmatrix}$

determined. Based on the determined column vector, new sphericalcoordinates are determined as:

$\quad\left\{ \begin{matrix}{\theta_{1} = {{arc}\; {{tg}\left( \frac{\sqrt{x_{1}^{2} + y_{1}^{2}}}{z_{1}} \right)}}} \\{\phi_{1} = {{arc}\; {{{tg}\left( \frac{y_{1}}{x_{1}} \right)}.}}}\end{matrix} \right.$

Thus, the azimuth of the point corresponds to φ₁, and the angle ofinclination

$\theta_{1} - {\frac{\pi}{2}.}$

corresponds to. That is, a, v are determined from the known p and t andEuler angles α, β, γ.

Inverse Problem

In order to determine the Euler angles based on the known relations oforientations in the inherent and absolute coordinate systems, it isnecessary to solve the problem which is inverse to the above directproblem.

For the inverse problem, namely for finding the Euler angles, let usdescribe the rotation of the system by using quaternions. In this case,“quaternion” is a quadruple of numbers (x, y, z, w), where (x, y, z) isa vector, and w is a scalar. In this representation of the quaternion,the first three components represent a vector which belongs to therotation axis, where the vector length depends on the rotation angle.The fourth component depends only on the value of the rotation angle.The dependence is quite simple—if we take the unit vector V for therotation axis and the angle alpha for rotation around this axis, thenthe quaternion representing this rotation can be written as follows:

q=[V*sin(alpha/2), cos(alpha/2)].

The initial data of the inverse problem are two pairs of mutuallyrelated vectors, namely (p₁, t₁)→(a₁, v₁) and (p₂, t₂)→(a₂, v₂), where(p, t) are the coordinates in the video camera's native coordinatesystem, and (a, v) are the coordinates in the video camera's absolutecoordinate system. Let us translate each of these vectors into theCartesian coordinate system, and we obtain the corresponding vectors:(x_(i), y_(i), z_(i))→(u_(i), v_(i), w_(i)), i=1, 2.

Now we will find the rotation quaternion of the camera initialcoordinate system that transforms the vector (x₁, y₁, z₁) into (u₁, v₁,w₁). This quaternion will describe the shortest distance rotation. Tofind it, we use the following formulas:

(x₁, y₁, z₁){circle around (×)} (u₁, v₁, w₁)=(a, b, c) is the crossproduct of the input vector by the final vector;

q=[a, b, c, (x₁, y₁z₁)(u₁, v₁, w₁)] is the sought quaternion (here (x₁,y₁, z₁)(u₁, v₁, w₁) is the scalar product of the vectors).

And in the last step let us normalize the quaternion q: to this end, wedivide x, y, z, w included thereby by n={square root over(x²+y²+z²+w²)}.

The quaternion obtained in this step defines the rotation of theCartesian coordinate system that translates (x₁, y₁, z₁) into (u₁, v₁,w₁).

Let us rotate the coordinate system, and, to this end, we use therotation formula: V′=qvq⁻,where v is the original vector, and V′ is thevector after the rotation. Thus, after the rotation of the Cartesiancoordinate system by the quaternion q we have two vectors: (u₁, v₁, w₁)obtained from (x₁, y₁, z₁), and a certain vector (u_(p), v_(p), w_(p))obtained from (x₂, y₂, z₂). Now, it is necessary to rotate the Cartesiancoordinate system in such a way that the vector (u₁, v₁, w₁) remains inplace, and the vector (u_(p), v_(p), w_(p)) transitions into a vector(u₂, v₂, w₂) (in general, it is possible not for any vectors, but as wetake their values from the real system, we believe that such a rotationis possible).

Obviously, in order to perform such a rotation, it is necessary that therotation axis passes through the point (u₁, v₁, w₁) and the origin ofcoordinates. To find the rotation angle, we will find the angulardistance on the sphere between two points (u_(p), v_(p), w_(p)) and (u₂,v₂, w₂). To this end, let us translate them into the sphericalcoordinate system: →(φ₁, λ₁) and (φ₂, λ₂), respectively. Then, we usethe formula for finding the angular distance (this formula is widelyused, for example, in astronomy):

${\Delta\sigma} = {\arctan \left\{ \frac{\sqrt{\left\lbrack {\cos \; \varphi_{2}\sin \; {\Delta\lambda}} \right\rbrack^{2} + \left\lbrack {{\cos \; \varphi_{1}\sin \; \varphi_{2}} - {\sin \; \varphi_{1}\cos \; \varphi_{2}\cos \; {\Delta\lambda}}} \right\rbrack^{2}}}{{\sin \; \varphi_{1}\sin \; \varphi_{2}} + {\cos \; \varphi_{1}\cos \; \varphi_{2}\cos \; {\Delta\lambda}}} \right\}}$

where Δλ is the difference between the coordinates in longitude, thatis, the difference between the coordinates in the angle λ, and Δσ is theangular difference.

Using the obtained angle and knowing the rotation axis, we obtain therotation quaternion that transforms the vector (u_(p), v_(p), w_(p))into (u₂, v₂, w₂): q₂=[(u₁, v₁, w₁)*sin(Δσ/2), cos(Δσ/2)]

Thus, we have obtained two rotation quaternions, q and q₂ which, whenapplied sequentially, transform the original points (x_(i), y_(i),z_(i)) into (u_(i), v_(i), w_(i)), i=1, 2. According to the definitionand properties of quaternions, the rotation quaternion, which isequivalent to two successive applications q and q₂, is equal to q₂*q. Wedenote it as Q=[X, Y, Z, W].

Next, we use the known formula for translating the quaternion into theEuler angles to obtain:

$\quad\left\{ \begin{matrix}{\alpha = {{arc}\; {{tg}\left( \frac{{2{XW}} - {2{XZ}}}{1 - {2Y^{2}} - {2Z^{2}}} \right)}}} \\{\beta - {\arcsin \left( {{2{XY}} + {2{ZW}}} \right)}} \\{\gamma - {{arc}\; {{tg}\left( \frac{{2{XW}} - {2{YZ}}}{1 - {2X^{2}} - {2Z^{2}}} \right)}}}\end{matrix} \right.$

This calculation can be done with sufficient accuracy, since theastronomical object position can be estimated with the accuracy of up tofew tenths/hundredths of a degree, according to the aforesaid.

It should be noted that the above-described automatic binding methoddoes not have to rely solely on an astronomical object(s). From theabove description, it should be apparent to those skilled in the artthat substantially any discernible object, whose position in the videocamera's absolute coordinate system is known or can be determined at agiven time(s) with sufficient accuracy, can act as the astronomicalobject. Any discernible still object visible in the terrain may serve assuch object, which is exemplified below.

The above procedure 200 is implemented, at least partially (i.e., atleast, its steps 206, 208), in the form of a computer-implementedmodule. The computer-implemented module is preferably software that canbe, in a local or distributed manner, stored in memory units and run byprocessors at the server 140, and/or the computer of the operatorworkstation 120, and/or the transmission-side equipment 111, dependingon the design of the system 100. At the same time, thecomputer-implemented module may also represent a hardware or firmwareunit (e.g., a blade server in a blade server chassis or a singlecomputing device), which should be obvious for those skilled in the art.The above software can be developed using an appropriate programmingtechnology chosen from a plurality of available technologies.

2. Correction to the Video Camera Binding

In order to provide the capability of filtering out false objects uponresponse from automatic detection algorithms, it is necessary toaccurately determine the direction to a previously detected object as itis detected again. This task is complicated by the fact that the camerabinding changes for various reasons, that is, the orientation of thenative coordinate system of the video camera (rotating device) changesin the absolute (horizontal) coordinate system associated with the videocamera location.

In order to eliminate the influence of this effect on the accuracy ofdetermining the direction to an object when it is detected again, it isnecessary to determine how the orientation of the video camera's nativecoordinate system in the absolute coordinate system has changed for theperiod elapsed between the repeated detections of the object.

To this end, it is proposed to use the objects visible in the terrainwhich are certainly known as not changing their position or changing itslightly (i.e. they are substantially still). These objects can be anyvisible stationary objects (e.g., window shutters, road signs, etc.).

Below with reference to FIG. 4, there is described the method 400implemented by the forest fire video monitoring system (such as thesystem 100 of FIG. 1) according to the present invention for determininga change in binding of the video camera,.

In step 402, the video camera is aimed at each of at least twopredefined discernible still objects in the terrain, and an orientationof the video camera in the video camera's native coordinate system isdetermined.

In step 404, the video camera orientations determined in step 402 arestored. The determined orientations can be stored in the storage devicecomprised by the server 140 and/or the computer of the operatorworkstation 120.

If verification is necessary, the following sub-steps are performed instep 406 for each of said still objects. In sub-step 406-1, the videocamera is aimed according to the video camera orientation stored in step404 that corresponds to said object. In sub-step 406-2, if during theperiod between the aimings at the object the video camera has displaced(for example, due to the possible reasons indicated above), then thevideo camera is re-aimed at the object and its current orientation inthe video camera's native coordinate system is determined.

In step 408, based on the video camera current orientations determinedin sub-step 406-2 and the respective video camera orientations stored instep 404, the rotation of the video camera's native coordinate system iscalculated that defines the correction for the aforementioned videocamera displacement. In fact, the rotation of the video camera's nativecoordinate system at the time of performing step 406 relative to thevideo camera's native coordinate system at the time of performing step402 is substantially determined.

Subsequently, for example, when the video camera detects a potentiallydangerous object, the current camera orientation is compared to theorientation determined based on the previously stored camera orientationto the object previously marked as non-dangerous and based on thecalculated rotation of the video camera's native coordinate system.

The possible implementation of steps 402-408 by means of the componentsof the system 100 is indicated above or obviously follows from thedescription of said system.

It should be obvious to those skilled in the art that in implementationof the above procedure 400 more than two stationary objects can be used.The number of such objects is generally defined by the requiredaccuracy—in particular, if the number of the objects increases, weincrease the number of independently obtained measurement results, whichleads, with appropriate processing, to the increased directiondetermination accuracy.

As described above, in order to determine the rotation, it is necessaryto determine the Euler angles which in this case will describe therotation of the video camera's native coordinate system for the currenttime moment relative to the video camera's native coordinate systemfixed during the preceding procedure of saving the orientation.

The mathematical problem is identical to that described above, both inessence and in the sense of complexity.

Let us suppose that the camera has slightly displaced, i.e. a visibleobject that has had the one coordinates in the video camera's nativecoordinate systems, namely (p11, t11) (which have been preliminarilysaved), now has the other coordinates, namely (p12, t12). We thus obtainthe correspondences:

(p11, t11)−(p12, t12),

(p21, t21)−(p22, t22)

Based on these correspondences, the Euler angles are determined similarto the above, i.e.

e1=f1(p11, t11, p12, t12,p21, t21,p22, t22),

e2=f2(p11, t11, p12, t12,p21, t21,p22, t22),

e3=f3(p11, t11, p12, t12,p21, t21,p22, t22).

After finding the Euler angles (e1, e2, e3) for each of the previouslymarked objects (e.g. as non-dangerous), given the stored video cameraorientation to this object (p1, t1), the adjusted orientation of thevideo camera to said object (pn, tn), i.e. the orientation adjusted forthe video camera displacement, can be determined as follows:

pn=f1(e1, e2, e3, p1, t1),

tn=f2(e1, e2, e3, p1, t1)

according to the method described above, when compared to the currentorientation of the camera.

For the most accurate operation of the system, the binding procedure 400can be performed before each patrolling; this procedure is expected notto take much time (few seconds).

Referring to FIG. 5, the method 500 for filtering observed objects,which involves the above method 400, may operate as follows.

During the patrolling, the video camera inspects the territory; theautomatic algorithm for detection of dangerous objects identifies apotentially dangerous object (step 501) in the video image. Upon this,the current orientation of the camera is identified (step 502). Further,the detected object is validated in some manner—for example, theoperator himself performs the validation, which may consist in visualrepresentation of the potentially dangerous object to the operator whoshould confirm or refute danger of the detected object (step 503). Afterthat, the system continues to patrol along the specified path (step504).

After some time defined by the class of fire danger and requirements forthe detection rate (for example, every 15 minutes), the system onceagain starts travelling the path (step 506). Before this, the procedureof determining changes in binding of the video camera is performedaccording to the above method 400 (step 505).

When a potentially dangerous object is detected, the orientation of thevideo camera to said object is determined and compared with the storedvideo camera orientation to an object(s) which was designated asnon-dangerous in the past patrolling(s) that is adjusted based on thecomputed rotation of the video camera's native coordinate system (step507). If the orientations coincide with the pre-specified accuracydefined by the system settings (e.g., up to 0.01′), then the system doesnot generate a new alarm for the operator and does not requirevalidation, and continues to patrol (step 508). This method cansignificantly reduce the operator workload, increase the number ofcameras per operator, and reduce the number of false alarms.

The above procedure 400 is implemented, at least partially (i.e. atleast, its step 408), in the form of a computer-implemented module. Thecomputer-implemented module is preferably software that can be, in alocal or distributed manner, stored in memory units and run byprocessors at the server 140, and/or the computer of the operatorworkstation 120, and/or the transmission-side equipment 111, dependingon the design of the system 100. At the same time, thecomputer-implemented module may also be a hardware or firmware unit(e.g., a blade server in a blade server chassis or a single computingdevice), which should be obvious for those skilled in the art. The abovesoftware can be developed using an appropriate programming technologychosen from a plurality of available technologies.

The invention has been described above with reference to specificembodiments thereof. For those skilled in the art other embodiments ofthe invention should be obvious that fall within the spirit and scope ofthe present invention, as it is disclosed herein. Accordingly, theinvention should be regarded as limited in scope only by the followingclaims.

1. A forest fire video monitoring system comprising: at least oneremotely controlled video monitoring point which includes a high-riseconstruction and a transmission-side equipment residing on the high-riseconstruction, the transmission-side equipment comprising: a video cameraon a rotating device; and a camera control unit configured to determinea current spatial orientation of the video camera in a native coordinatesystem of the video camera; at least one computerized operatorworkstation for operating said video monitoring point; and acomputer-implemented module configured: in each of at least twopredetermined time moments, to obtain an orientation of the video cameraaimed at a known astronomical object, said orientation determined by thecamera control unit in the native coordinate system of the video camera,and to determine, based on a predetermined location of the videomonitoring point and said time moment, a position of the astronomicalobject in the absolute coordinate system centered in a point in whichthe video camera resides, and to calculate, based on the determinedorientations of the video camera and positions of the astronomicalobject, a rotation of the native coordinate system of the video camerain the absolute coordinate system.
 2. The system of claim 1, wherein thetransmission-side equipment of said video monitoring point furthercomprises a communication device, wherein the system further comprises aserver, and wherein the video monitoring point, the server, and theoperator workstation are communicatively connected to each other.
 3. Thesystem of claim 2, wherein the video camera of the transmission-sideequipment of said video monitoring point is equipped with a zoom.
 4. Thesystem of claim 3, wherein the video camera is aimed at the astronomicalobject by manually matching the center of an image obtained from thevideo camera with the center of the astronomical object.
 5. The systemof claim 3, further comprising a computer-implemented intelligentsubsystem configured, based on computer vision technologies, to aim thevideo camera at the astronomical object by automatically detecting theastronomical object based on analysis of an image obtained from a videocamera, and automatically matching the center of the image obtained fromthe video camera with the center of the astronomical object.
 6. Thesystem of claim 4, wherein, when aiming the video camera at theastronomical object, the zoom is used to zoom in the astronomical objectto the maximum possible extent.
 7. The system of claim 2, wherein saidcomputer-implemented module resides at the server, and/or said operatorworkstation, and/or the transmission-side equipment of said videomonitoring point.
 8. The system of claim 1, wherein the astronomicalobject is Sun.
 9. The system of claim 1, wherein the native coordinatesystem of the video camera is defined by a manufacturer of the videocamera.
 10. The system of claim 1, wherein the location of said videomonitoring point is defined by its geographical coordinates, and theposition of the astronomical object is defined by its azimuth andangular altitude above the horizon.
 11. The system of claim 1, whereinthe calculated rotation of the native coordinate system of the videocamera is used to recalculate coordinates of an observed object from thenative coordinate system of the video camera into the absolutecoordinate system.
 12. In a forest fire video monitoring systemcomprising at least one remotely controlled video monitoring pointcomprising: a video camera on a rotating device residing on a high-riseconstruction; and a camera control unit configured to determine acurrent spatial orientation of the video camera in a native coordinatesystem of the video camera, a method for automatically binding thenative coordinate system of the video camera to an absolute coordinatesystem, the method comprising the steps of: in each of at least twopredetermined time moments aiming the video camera at a knownastronomical object, and determining an orientation of the video camerain the native coordinate system of the video camera, and determining,based on a predetermined location of the video monitoring point and saidtime moment, a position of the astronomical object in the absolutecoordinate system centered in a point in which the video camera resides;and calculating, based on the determined orientations of the videocamera and positions of the astronomical object, a rotation of thenative coordinate system of the video camera in the absolute coordinatesystem.
 13. The method of claim 12, further comprising, based on thecalculated rotation of the native coordinate system of the video camera,recalculating coordinates of an observed object from the nativecoordinate system of the video camera into the absolute coordinatesystem.
 14. The method of claim 12, wherein the video camera is aimed atthe astronomical object by manually matching the center of an imageobtained from the video camera with the center of the astronomicalobject.
 15. The method of claim 12, wherein the video camera is aimed atthe astronomical object by automatically detecting the astronomicalobject based on analysis of an image obtained from the video camera andautomatically matching the center of the image obtained from the videocamera with the center of the astronomical object, based on computervision technologies.
 16. A forest fire video monitoring systemcomprising: at least one remotely controlled video monitoring pointwhich includes a high-rise construction and a transmission-sideequipment residing on the high-rise construction, the transmission-sideequipment comprising: a video camera on a rotating device; and a cameracontrol unit configured to determine a current spatial orientation ofthe video camera in a native coordinate system of the video camera; atleast one computerized operator workstation for operating said videomonitoring point; and a computer-implemented module configured: in eachof at least two predetermined time moments, to obtain an orientation ofthe video camera in the native coordinate system of the video camera,wherein the orientation is determined by the camera control unit whenthe video camera is aimed at a known astronomical object, wherein aposition of the astronomical object in an absolute coordinate systemcentered in a point in which the video camera resides is known at saidtime moment, to calculate, based on the determined orientations of thevideo camera and positions of the astronomical object, a rotation of thenative coordinate system of the video camera in the absolute coordinatesystem.
 17. In a forest fire video monitoring system comprising at leastone remotely controlled video monitoring point comprising: a videocamera with a rotating device residing on a high-rise construction; anda camera control unit configured to determine a current spatialorientation of the video camera in a native coordinate system of thevideo camera, a method for automatically binding the native coordinatesystem of the video camera to an absolute coordinate system, the methodcomprising the steps of: in each of at least two predetermined timemoments, aiming the video camera at an object a position of which in theabsolute coordinate system centered at a point in which the video cameraresides is known at said moment, and determining an orientation of thevideo camera in the native coordinate system of the video camera; andbased on the determined orientations of the video camera and positionsof the object, calculating a rotation of the native coordinate system ofthe video camera in the absolute coordinate system.
 18. A forest firevideo monitoring system comprising: at least one remotely controlledvideo monitoring point which includes a high-rise construction and atransmission-side equipment residing on the high-rise construction, thetransmission-side equipment comprising: a video camera on a rotatingdevice; and a camera control unit configured to determine a currentspatial orientation of the video camera in a native coordinate system ofthe video camera; at least one computerized operator workstation foroperating said video monitoring point; a storage device for storingorientations of the video camera in the native coordinate system of thevideo camera, the orientations determined by the camera control unitupon aiming the video camera at each of at least two predetermineddiscernible still objects in the terrain; and a computer-implementedmodule configured: for each of said objects, to obtain a currentorientation of the video camera in the native coordinate system of thevideo camera, the orientation determined by the camera control unit uponre-aiming the video camera at said object, and based on the obtainedcurrent orientation of the video camera and the respective storedorientations of the video camera, to calculate a rotation of the videocamera native coordinate system.
 19. The system of claim 18, wherein thecomputer-implemented module is further configured, when comparing acurrent orientation of the video camera aimed at an observed object witha stored orientation of the video camera when aimed at a previouslyanalyzed object, to adjust said stored camera orientation based on thecalculated rotation of the native coordinate system of the video camera.20. In a forest fire video monitoring system comprising at least oneremotely controlled video monitoring point including: a video camerawith a rotating device residing on a high-rise construction; and acamera control unit configured to determine a current spatialorientation of the video camera in a native coordinate system of thevideo camera, a method for determining changes in binding of the videocamera, the method comprising the steps of: aiming the video camera ateach of at least two predetermined discernible still objects in theterrain, and determining an orientation of the video camera in thenative coordinate system of the video camera; storing the determinedorientations of the video camera; for each of said objects: aiming thevideo camera according to the stored orientation of the video cameracorresponding to said object, and, in case of deviation of the videocamera from the object, re-aiming the video camera at the object, anddetermining a current orientation of the video camera in the nativecoordinate system of the video camera; and based on the determinedcurrent orientations of the video camera and the respective storedorientations of the video camera, calculating a rotation of the nativecoordinate system of the video camera.
 21. The method of claim 20,wherein the method comprises, when comparing a current orientation ofthe video camera aimed at an observed object with a stored orientationof the video camera when aimed at a previously analyzed object,adjusting said stored camera orientation based on the calculatedrotation of the native coordinate system of the video camera.
 22. Thesystem of claim 5, wherein, when aiming the video camera at theastronomical object, the zoom is used to zoom in the astronomical objectto the maximum possible extent.